The montane butterflies of the eastern Afrotropics - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 162

a belt in the Qu aternary. If such a belt ever
eisted, the traces have been wiped out. Similarly,
there is no evidence or a former coninuous
montane forest belt from East Africa to
Cameroun. The rather small proporion of taxa of
the montane forests of EAT also occurring in
Cameroun can equally well be explained by range
extensions through unsaturated forests at low and
medium elevations. The majority if not all of the
Afromontane butterflies in EAT did not originate
from colonisation from elsewhere but by differen-
iation and switches in habitat preference within
EAT. There is no evidence that the switches were
attributable to or accompanied by geographic
isolaion. The age of the Easten Arc mountains is
reflected in their high diversity. Once adapted to
the montane forests the species more or less
spread over the mountain ranges. Locally the
spread may have been facilitated by temporary
extensions of the forest, but the butterflies do not
indicate a repeated vicariance scenario. It rather
seems that dispersal and local exincions have led
to the present disribuion patten.

Easten Arc mountains and the Westen Border
Range. A combinaion of both scenarios leads to a
patten of either many shared species or many
sister species in both the Eastern Arc mountains
and the Western Border Range. As already men-
ioned there are few widespread species: only five
species (2.8%) occur in seven or all eight com-
bined areas (Table 8.5). No monophyleic groups
of allopatric species are known, but there are
some monophyletic groups the species of which
together cover most of the mountain ranges, like
Papilio honimani-charopus-mackinnoni and the
five Ch ondrolepis species. Their number, however,
hardly reinforces the patten of widespread taxa.
Equally, there is no evidence for a strong
similarity between the Easten Arc mountains and
the Westen Border Range. Of the 146 species
occurring in one or both of these ranges only 10
(7%) are common to both. The only known twin
relaionship between the Easten Arc mountains
(in this case with north Tanzania) and the
Western Border Range is the Biyclus anckelmani
group. Even though the exact relaionships in this
group are not known the distribution of the spe-
cies (Figure 8.4) shows that an Easten Arc
mountains-Western Border Range twin relaion-
ship must occur here.
On the basis of the patterns found we can only
conclude that there is no evidence of a former
continuous montane forest habitat. It has even
proved difficult to combine areas into larger units,
this usually being based on the distribuion of a
few species only. It points rather to a dispersal
than to a fragmentaion scenario. Patten (ii) on
the other hand agrees well with what is really
ound: high concenraions of species in the
Eastern Arc mountains and the Westen Border
Range, and far fewer elsewhere. It is paricularly
obvious in the endemics (see Table 8.5). Conse-
quently we cannot refute the hypothesis of a
large-scale extincion of montane forest species in
many mountains of EAT.

Sumay

The distribuion of the butterflies more or less
restricted to montane habitats in the Easten
Afrotropics (EAT; roughly east of Long. 30° E) is
analysed. Two habitats are invesigated in some
detail: montane grasslands and montane forests.
There are no butterlies characterisic of the tree-
less Afroalpine zone. The few butterflies that are
found there have come from lower elevaions,
possibly using air currents. It is not clear why
there are no Afroalpine butterflies: there may be
an ecological rather than a historical origin.
It is concluded that a small proporion (/4 to
Is) of the montane grassland butterflies origin-
ated from dispersal from the Palaearcic and
Oriental regions. By far the greater part, however,
originated in the Easten Afrotropics rom species
with other habitat preferences. The montane for-
est fauna of the area has no affinity with montane
forest faunas elsewhere except for Cameroun.
The similarity (limited, as far as the Easten
Afrotropics are concened) between the montane
forest faunas of Cameroun and the easten part of

onlusion

The butterflies that are more or less restricted to
the montane forests of EAT do not bear evidence
of a Teriay forest belt across Africa, nor of such